At present, and as shown very schematically in FIGS. 1 and 2, the fore-structure of a wide body freight aircraft comprises a pressurized compartment 1 that is extended forward by a radome 2 that contains a radar chamber 3. Inside pressurized compartment 1 a plane floor 4 supports the cockpit and the freight accommodation. One or more access doors 5 can be provided under the fuselage in the pressurized zone behind radar chamber 3 to enable ground staff to enter the section of pressurized compartment 1 located under floor 4, in order to carry out standard maintenance operations.
In pressurized zone 5, an unpressurized landing gear compartment 6 is provided in the fuselage to receive the fore landing gear 7 in the retracted position. The landing gear compartment 6 is separated from pressurized compartment 1 by a certain number of partitions. The partitions include two lateral partitions that are more or less vertical, a fore partition, a rear partition as well as a ceiling that is often sloped towards the bottom working from the fore to the rear when the wheels are in front of the anchoring fittings of the strut of the undercarriage in the retracted position.
Depending on the aircraft, it may be noted that designers generally aim to reduce the size of the landing gear compartment by using shapes that are more or less complex or elaborate in order to increase, among other aims, the available space in the pressurized zone. However, in all these designs the layout of the fore structure remains standard and the other problems still exist.
The standard layout of the fore structure of freight aircraft is described in FIGS. 11.4.3 and 11.4.4 (page 400) of Chun Yung Nui's "Airframe Structural Design", which is the standard authority in the field of aeronautical structural design.
The standard layout does, however, present a certain number of drawbacks.
For instance, access to radar chamber 3 is only possible from the outside by dismantling radome 2. This operation, that is indispensable for any maintenance, repair or test work on the radar antenna, always requires the use of screws and/or hinges to fasten radome 2 to the aircraft. In order to carry out this operation, the system for fastening the radome requires a permanent degree of play. Consequently, there are inevitable projections between the edges of radome 2 and the aircraft structure. The projections, which are significant, or at least cannot be discounted, are located in a crucial zone. This results in aerodynamic drag interference and may disturb the anemometric air vents located near the raydome.
Moreover, the access doors 5 that are used by the ground staff in order to enter the lower section of pressurized compartment 1, give onto the exterior of the aircraft. The projections that are inevitably present between the door and the aircraft structure also cause aerodynamic drag that reduces aircraft performance.
Another drawback of the standard layout of the fore structure of aircraft is due to the shape of landing gear compartment 6. The spaces between the surfaces of the aircraft and the lateral surfaces of the landing gear compartment are often limited and, consequently, almost unusable. However, these spaces are pressurized and require structural reinforcement parts in order to readjust to pressurization.
Finally, the standard design of landing gear compartment 6 limits the volume available, especially for the wheels and the tires of the fore landing gear 7, and may prevent larger wheels from being mounted in the event of the aircraft being upgraded. In a very wide-body aircraft, the maximum mass of which may exceed 500 tonnes at take off, the load to which the fore landing gear is subject requires wheels and tires of measurements that are no longer compatible with a standard design landing gear compartment.